The subject matter disclosed herein generally relates to X-ray imaging techniques and, in particular, to systems and methods for reconstructing images in X-ray phase contrast imaging.
In non-invasive imaging systems, X-ray tubes are used in various X-ray systems and computed tomography (CT) systems as a source of X-ray radiation. The radiation is emitted in response to control signals during an examination or imaging sequence. Typically, the X-ray tube includes a cathode and an anode. An emitter within the cathode may emit a stream of electrons in response to heat resulting from an applied electrical current, and/or an electric field resulting from an applied voltage to a properly shaped metallic plate in front of the emitter. The anode may include a target that is impacted by the stream of electrons. The target may, as a result of impact by the electron beam, produce X-ray radiation to be emitted toward an imaged volume.
Conventional X-ray imaging systems may detect an imaged volume based on absorption of the X-ray radiation. However, absorption-based techniques may provide images with insufficient distinction between certain types of tissue structures. For example, tumors and fluid-filled cysts may be difficult to distinguish on images generated by X-ray absorption of tissue. Other techniques, such as phase contrast techniques, may provide images with more contrast between different types of tissue structures. However, image reconstruction associated with such techniques may be subject to a variety of drawbacks associated with factors such as image geometry, hardware constraints, and so forth.
For example, in grating based differential X-ray phase contrast techniques, the obtained measurement generates projections of the gradient of the cumulative phase shift due to refractive index variability of the subject in a direction orthogonal to the X-ray beam and to the grating slits, thus resulting in projections that have a differential nature. In order to visualize these projections for diagnostic purposes, an integration step is required. Unfortunately, the noisy nature of the data may complicate the integration step, thereby resulting in blurred images having streak artifacts along the line of integration. Accordingly, there exists a need for imaging and methods that address these drawbacks.